Why is it a bad idea you ask?As you may know any food such as your wedding cake has a finite lifetime. Most items that are frozen are sealed to keep out external flavors and moisture. The sealed items can easily last a year in the freezer. With a wedding cake you can seal the wedding cake in a container, if you have one that is large enough. If not the flavors and smells will "leak" into your cake changing the taste. The frosting may also become hard from moisture leaving and entering the spongy cake itself.
The options you actually have are few to actually save your wedding cake for an entire year, some people opt to have it as dessert with dinner to avoid the unfortunate result of having cake that has many flavors and smells of other food in the fridge
Most people also do not own a food saver or air sealer. If you do try to save the cake in a air sealing device, the wedding cake will become compressed and basically turn into a large hard block.